Comparison of four low-level carbon monoxide alarms suitable for home use or when traveling.

Introduction: Interest in carbon monoxide (CO) alarms that are more sensitive than is required for standard residential CO alarms is growing, as reflected by increased marketing of "low-level" alarms capable of measuring CO levels as low as 10 PPM. At the same time, publicity surrounding CO poisoning events among travelers in lodging facilities has stimulated interest in travel CO alarms. We sought to evaluate four low-level alarms that could be used in the home and especially when traveling. Materials/Methods: Two each of four brands of low-level alarms (CO Experts, Forensics, Kidde, and Sensorcon) were acquired by retail purchase and tested. The eight alarms were simultaneously exposed in an environment with a slowly increasing level of CO from indoor burning of charcoal briquets. CO levels displayed on the alarms were recorded once per minute. Activation of preset alerts on the alarms were noted. Finally, alarms were compared for ease of use and features available.. Results: All brands of alarms measured CO similarly over the range from 10-120 PPM. All alarms performed as claimed by their manufacturers, both regarding range of CO reported and preset alert activation. Each alerted at CO levels below that required by the Underwriters Laboratories 2034 Standard. Summary/Conclusion: Since all low-level CO alarms tested measured CO similarly, consumers seeking a low-level CO alarm for use while traveling should base their decision on features desired and price. There are definite differences between the alarms tested, in terms of features, expected durability, ease of operation and price.

Stability of residual hearing and cochlear implant function following multiple scuba dives: case report.

OBJECTIVES: There are limited data regarding the safety of cochlear implants during exposure to pressure changes associated with scuba and hyperbaric oxygen therapy. There are no data regarding the effects of barometric pressure changes on preserved low-frequency hearing after cochlear implantation. This case report evaluates the effect of barometric pressure changes on preserved low-frequency hearing after cochlear implantation. PATIENT: This is a case report of a patient who underwent successful cochlear implantation with postoperative preservation of residual low-frequency hearing. INTERVENTIONS: 20 scuba dives up to depths of 92 feet (3.8 atmospheres absolute). RESULTS: Audiometric testing both before and after scuba shows no change in hearing thresholds. The internal receiver-stimulator of the cochlear implant was unaffected by prolonged and repeated pressures up to approximately 3.8 atmospheres absolute. The patient had no adverse middle ear effects during or after the dives, and no evidence of inner ear barotrauma or decompression sickness as a result of the elevated pressures. CONCLUSIONS: This is the first report of preserved hearing after cochlear implantation being maintained following scuba diving, and corroborates previous literature showing that exposure to increased pressures with a cochlear implant in situ is safe without adverse effects on the implant hardware or software. Scuba diving appears safe not only with cochlear implants but also in patients with residual hearing.

Consensus guideline: Pre-hospital management of decompression illness: expert review of key principles and controversies.

(Mitchell SJ, Bennett MH, Bryson P, Butler FK, Doolette DJ, Holm JR, Kot J, Lafère P. Pre-hospital management of decompression illness: expert review of key principles and controversies. Diving and Hyperbaric Medicine. 2018 March;48(1):45е.doi.10.28920/dhm48.1.45-55.) Guidelines for the pre-hospital management of decompression illness (DCI) had not been formally revised since the 2004 Divers Alert Network/Undersea and Hyperbaric Medical Society workshop held in Sydney, entitled "Management of mild or marginal decompression illness in remote locations." A contemporary review was initiated by the Divers Alert Network and undertaken by a multinational committee with members from Australasia, the USA and Europe. The process began with literature reviews by designated committee members on: the diagnosis of DCI; first aid strategies for DCI; remote triage of possible DCI victims by diving medicine experts; evacuation of DCI victims; effect of delay to recompression in DCI; pitfalls in management when DCI victims present at hospitals without diving medicine expertise and in-water recompression. This was followed by presentation of those reviews at a dedicated workshop at the 2017 UHMS Annual Scientific Meeting, discussion by registrants at that workshop and, finally, several committee meetings to formulate statements addressing points considered of prime importance to the management of DCI in the field. The committee placed particular emphasis on resolving controversies around the definition of "mild DCI" arising over 12 years of practical application of the 2004 workshop's findings, and on the controversial issue of in-water recompression. The guideline statements are promulgated in this paper. The full workshop proceedings are in preparation for publication.

Garage carbon monoxide levels from sources commonly used in intentional poisoning.

BACKGROUND: The incidence of intentional carbon monoxide (CO) poisoning is believed to have declined due to strict federal CO emissions standards for motor vehicles and the uniform application of catalytic converters (CC). We sought to compare ambient CO levels produced by automobiles with and without catalytic converters in a residential garage, as well as from other CO sources commonly used for intentional poisoning. METHODS: CO levels were measured inside a freestanding 73 m3 one-car garage. CO sources included a 1971 automobile without CC, 2003 automobile with CC, charcoal grill, electrical generator, lawn mower and leaf blower. RESULTS: After 20 minutes of operation, the CO level in the garage was 253 PPM for the car without a catalytic converter and 30 PPM for the car equipped withone. CO levels after operating or burning the other sources were: charcoal 200 PPM; generator >999 PPM; lawn mower 198 PPM; and leaf blower 580 PPM. CONCLUSIONS: While emissions controls on automobiles have reduced intentional CO poisonings, alternate sources may produce CO at levels of the same magnitude as vehicles manufactured prior to the use of catalytic converters. Those involved in the care of potentially suicidal individuals should be aware of this.

Suicidal carbon monoxide poisoning has decreased with controls on automobile emissions.

BACKGROUND: Highway vehicle CO emissions have decreased 85% since introduction of the catalytic converter in 1975. We sought to examine whether morbidity and mortality from intentional motor vehicle-related CO poisoning have also changed. METHODS: Vehicle CO emissions data from 1970-2013 were obtained from the U.S. Environmental Protection Agency. U.S. Centers for Disease Control and Prevention data were used for the suicide crude death rate (CDR) from CO poisoning from 1999-2010. Data on non-fatal intentional CO poisonings treated at a regional hyperbaric treatment center from 1981-2013 were analyzed with regard to numbers treated and presenting carboxyhemoglobin (COHb) levels. RESULTS: Since 1985, the CDR for suicidal motor vehicle-related CO poisoning has decreased in parallel with CO emissions (R2 = 0.985). Non-fatal motor vehicle-related intentional CO poisoning cases decreased 63% over 33 years (p = 0.0017). COHb levels decreased 35% in these patients (p < 0.0001). CONCLUSIONS: There has been a decrease in both fatal and non-fatal intentional CO poisoning from motor vehicle exhaust since the 1980s. This correlates with reductions in vehicle CO emissions and is a likely result of the U.S. Clean Air Act of 1970 and the application of catalytic converters since 1975.

Ambulatory measurement of ambient carbon monoxide levels.

BACKGROUND: Measurement of air pollutant levels in the environment is traditionally performed using monitors in fixed locations so that changes over time can be directly compared. Such measurements do not necessarily correlate with the level of exposure to the individual because of distance to the monitoring site and other factors. In the case of carbon monoxide (CO), portable personal monitors are available for industrial use, some of which do not just alarm, but also record measured values. OBJECTIVES: First, it was the purpose of this study to test the feasibility of continuously measuring ambient CO levels in an ambulatory fashion. The second objective was to compare measurements made in a country with significant air pollution to one without to determine the degree to which differences might be observed. METHODS: Ambient CO levels were measured and recorded every 10 minutes during 13 days of travel in Vietnam. A parallel study was performed in the United States for comnarison. RESULTS: Continuous ambient CO levels at an individual level were successfully measured and recorded. Mean ambient CO level throughout Vietnam was 3.5 ± 4.4 ppm, as compared to 0.9 ± 0.8 ppm in the U.S. (p < 0.001). In Vietnam, 36 CO measurements (2% of total) were 15 ppm or greater vs. none in the U.S. Higher mean levels, as well as number and magnitude of peaks, were highly associated with proximity to traffic. CONCLUSIONS: Personal exposures to CO can be measured easily over time and may be more relevant to the individual with underlying disease than data from fixed monitoring stations. Such information may prove useful to potential travelers. Additionally, governmental agencies may find ambulatory measurement to be complimentary to data from fixed monitoring stations when attempting to estimate how traditionally collected data relate to exposure of the individual. The technique could also be used for evaluation of vague complaints suggestive of intermittent CO exposure in the home or workplace.

Altitude exposures during commercial flight: a reappraisal.

BACKGROUND: Hypobaric hypoxia during commercial air travel has the potential to cause or worsen hypoxemia in individuals with pre-existing cardiopulmonary compromise. Knowledge of cabin altitude pressures aboard contemporary flights is essential to counseling patients accurately about flying safety. The objective of the study was to measure peak cabin altitudes during U.S. domestic commercial flights on a variety of aircraft. METHODS: A handheld mountaineering altimeter was carried by the investigators in the plane cabin during commercial air travel and peak cabin altitude measured. The values were then compared between aircraft models, aircraft classes, and distances flown. RESULTS: The average peak cabin altitude on 207 flights aboard 17 different aircraft was 6341 +/- 1813 ft (1933 m +/- 553 m), significantly higher than when measured in a similar fashion in 1988. Peak cabin altitude was significantly higher for flights longer than 750 mi (7085 +/- 801 ft) compared to shorter flights (5160 +/- 2290 ft/1573 +/- 698 m). Cabin altitude increased linearly with flight distance for flights up to 750 mi in length, but was independent of flight distance for flights exceeding 750 mi. Peak cabin altitude was less than 5000 ft (1524 m) in 70% of flights shorter than 500 mi. Peak cabin altitudes greater than 8000 ft (2438 m) were measured on approximately 10% of the total flights. CONCLUSIONS: Peak cabin altitude on commercial aircraft flights has risen over time. Cabin altitude is lower with flights of shorter distance. Physicians should take these factors into account when determining an individual's need for supplemental oxygen during commercial air travel.

Prospective assessment of outcomes in 411 patients treated with hyperbaric oxygen for chronic radiation tissue injury.

BACKGROUND: Although hyperbaric oxygen is used to treat chronic radiation tissue injury, clinical evidence supporting its efficacy has been limited to date. The authors report prospectively collected patient outcomes from a single center's large experience using hyperbaric oxygen to treat chronic radiation injury. METHODS: Since 2002, patient outcomes at the conclusion of a course of hyperbaric oxygen treatment for chronic radiation tissue injury at Virginia Mason Medical Center in Seattle have been graded by a board-certified hyperbaric physician and prospectively recorded. From 2002 to 2010, a total of 525 patients received treatment for 1 of 6 forms of radionecrosis analyzed. After excluding 114 patients for incomplete records or treatment courses or for previous receipt of hyperbaric oxygen therapy, records of 411 patients were retrospectively reviewed in 2010, and outcomes were regraded by a second board-certified physician. A positive clinical response was defined as an outcome graded as either "resolved" (90%-100% improved) or "significantly improved" (50%-89% improved). RESULTS: A positive outcome from hyperbaric treatment occurred in 94% of patients with osteoradionecrosis of the jaw (n = 43), 76% of patients with cutaneous radionecrosis that caused open wounds (n = 58), 82% of patients with laryngeal radionecrosis (n = 27), 89% of patients with radiation cystitis (n = 44), 63% of patients with gastrointestinal radionecrosis (n = 73), and 100% of patients who were treated in conjunction with oral surgery in a previously irradiated jaw (n = 166). CONCLUSIONS: The outcomes of 411 patients collected prospectively over 8 years strongly supported the efficacy of hyperbaric oxygen treatment for the 6 conditions evaluated. The response rates previously reported in numerous small series were supported by the responses achieved in this large, single-center experience.

Should the placement of carbon monoxide (CO) detectors be influenced by CO's weight relative to air?

BACKGROUND: Numerous states and localities have recently passed legislation mandating the installation and use of residential carbon monoxide (CO) detectors/alarms. Interestingly, there seems to be confusion about the optimal placement, if any, of CO alarms inside the home. OBJECTIVES: It was the goal of this study to demonstrate the behavior of CO in air and to help provide a data-based recommendation for CO alarm placement. METHODS: CO was calculated to be slightly lighter than air. An 8-foot-tall airtight Plexiglas chamber was constructed and CO monitors placed within at the top, middle, and bottom. CO test gas (15 L, 3000 parts per million) was infused at each of the three heights in different trials and CO levels measured over time. RESULTS: Contrary to a significant amount of public opinion, CO did not layer on the floor, float at the middle of the chamber, or rise to the top. In each case, the levels of CO equalized throughout the test chamber. It took longer to equalize when CO was infused at the top of the chamber than the bottom, but levels always became identical with time. CONCLUSIONS: As would have been predicted by the Second Law of Thermodynamics, CO infused anywhere within the chamber diffused until it was of equal concentration throughout. Mixing would be even faster in the home environment, with drafts due to motion or temperature. It would be reasonable to place a residential CO alarm at any height within the room.

Severe Decompression Sickness Associated with Shock and Acute Respiratory Failure.

Decompression sickness (DCS) is a well-recognized complication of diving but rarely results in shock or respiratory failure. We report a case of severe DCS in a diver associated with shock and respiratory failure requiring mechanical ventilation. A healthy 50-year-old male diver dove to a depth of 218 feet for 43 minutes while breathing air but omitted 6.5 hours of air decompression due to diver error. The clinical presentation was remarkable for loss of consciousness, hypotension, cutis marmorata, peripheral edema, and severe hypoxia requiring mechanical ventilation with diffuse lung opacities on chest radiograph. Laboratories were significant for polycythemia and hypoalbuminemia. A single hyperbaric oxygen treatment was provided on the day of admission during which shock worsened requiring aggressive volume resuscitation and three vasopressors. In the first 37 hours of hospitalization, 22 liters of crystalloid and multiple albumin boluses were administered for refractory hypotension by which time all vasopressors had been discontinued and blood pressure had normalized. He required 10 days of mechanical ventilation and was discharged on day 21 with mild DCS-related neurologic deficits. This clinical course is characteristic of DCS-related shock wherein bubble-endothelial interactions cause a transient capillary leak syndrome associated with plasma extravasation, hemoconcentration, and hypovolemia. The pathophysiology and typical clinical course of DCS-related shock suggest the need for aggressive but time-limited administration of crystalloid and albumin. Because hyperbaric oxygen is the primary treatment for DCS, treatment with hyperbaric oxygen should be strongly considered even in the face of extreme critical illness.

Evidence of Microbubbles on Kidney Stones in Humans.

The color Doppler ultrasound twinkling artifact has been found to improve detection of kidney stones with ultrasound; however, it appears on only ∼60% of stones. Evidence from ex vivo kidney stones suggests twinkling arises from microbubbles stabilized in crevices on the stone surface. Yet it is unknown whether these bubbles are present on stones in humans. Here, we used a research ultrasound system to quantify twinkling in humans with kidney stones in a hyperbaric chamber. Eight human patients with non-obstructive kidney stones previously observed to twinkle were exposed to a maximum pressure of 4 atmospheres absolute (ATA) while breathing air, except during the 10-min pause at 1.6 ATA and while the pressure decreased to 1 ATA, during which patients breathed oxygen to minimize the risk of decompression sickness. A paired one-way t-test was used to compare the mean twinkle power at each pressure pause with baseline twinkling, with p < 0.05 considered to indicate significance. Results revealed that exposure to 3 and 4 ATA of pressure significantly reduced twinkle power by averages of 35% and 39%, respectively, in 7 patients (p = 0.04); data from the eighth patient were excluded because of corruption. This study supports the theory that microbubbles are present on kidney stones in humans.

A phase 2B randomised trial of hyperbaric oxygen therapy for ulcerative colitis patients hospitalised for moderate to severe flares.

BACKGROUND: Hyperbaric oxygen has been reported to improve disease activity in hospitalised ulcerative colitis (UC) patients. AIM: To evaluate dosing strategies with hyperbaric oxygen for hospitalised UC patients. METHODS: We enrolled UC patients hospitalised for acute flares (Mayo score 6-12). Initially, all patients received 3 days of hyperbaric oxygen at 2.4 atmospheres (90 minutes with two air breaks) in addition to intravenous steroids. Day 3 responders (reduction of partial Mayo score ≥ 2 points and rectal bleeding score ≥ 1 point) were randomised to receive a total of 5 days vs 3 days of hyperbaric oxygen. RESULTS: We treated 20 patients with hyperbaric oxygen (75% prior biologic failure). Day 3 response was achieved in 55% (n = 11/20), with significant reductions in stool frequency, rectal bleeding and CRP (P < 0.01). A more significant reduction in disease activity was observed with 5 days vs 3 days of hyperbaric oxygen (P = 0.03). Infliximab or colectomy was required in only three patients (15%) despite a predicted probability of 80% for second-line therapy. Day 3 hyperbaric oxygen responders were less likely to require re-hospitalisation or colectomy by 3 months vs non-responders (0% vs 66%, P = 0.002). No treatment-related adverse events were observed. CONCLUSION: Hyperbaric oxygen appears to be effective for optimising response to intravenous steroids in UC patients hospitalised for acute flares, with low rates of re-hospitalisation or colectomy at 3 months. An optimal clinical response is achieved with 5 days of hyperbaric oxygen. Larger phase 3 trials are needed to confirm efficacy and obtain labelled approval.

The Role of Hyperbaric Oxygen as Salvage Therapy for Sudden Sensorineural Hearing Loss.

OBJECTIVE: We sought to evaluate hearing outcomes after salvage therapy with hyperbaric oxygen (HBO2) for the treatment of sudden sensorineural hearing loss (SSNHL). STUDY DESIGN: Matched control retrospective case series. SETTING: Tertiary neurotology referral center. PATIENTS: Thirty-six patients (>18 years) diagnosed with SSNHL. INTERVENTION: Patients received initial therapy with oral and/or intratympanic (IT) steroids with an incomplete response. Eighteen patients underwent salvage therapy with IT steroids and HBO2 (group 1). Eighteen matched controls underwent salvage therapy with IT steroids alone (group 2). MAIN OUTCOME MEASURES: The main outcome measure was improvement in pure tone average (PTA) and word recognition score (WRS). Complications as a result of therapy were also monitored. RESULTS: There were no significant differences in age, gender, or hearing between the 2 groups ( P > .05). There was no significant difference in mean post-treatment PTA between group 1 (60.3 dB) and group 2 (53.2 dB). There were no significant difference in mean post-treatment WRS between group 1 (42%) and group 2 (51%). Serviceable hearing was defined as a minimum WRS of 50%. Thirty-three percent in group 1 and 42% in group 2 went from nonserviceable hearing to serviceable hearing ( P > .05). PTA and WRS change scores were not significantly affected by age, gender, form of initial treatment, or pre-treatment PTA and WRS. CONCLUSION: The present study demonstrated no significant difference in hearing outcomes between patients receiving salvage therapy with HBO2 and IT steroids compared to patients receiving IT steroids alone. Larger, prospective randomized trials are needed to better define the role of HBO2 as salvage therapy for SSNHL.

Pre-hospital management of decompression illness: expert review of key principles and controversies.

Guidelines for the pre-hospital management of decompression illness (DCI) had not been formally revised since the 2004 Divers Alert Network/Undersea and Hyperbaric Medical Society workshop held in Sydney, entitled "Management of mild or marginal decompression illness in remote locations". A contemporary review was initiated by the Diver's Alert Network and undertaken by a multinational committee with members from Australasia, the USA and Europe. The process began with literature reviews by designated committee members on: the diagnosis of DCI; first aid strategies for DCI; remote triage of possible DCI victims by diving medicine experts; evacuation of DCI victims; effect of delay to recompression in DCI; pitfalls in management when DCI victims present at hospitals without diving medicine expertise and in-water recompression. This was followed by presentation of those reviews at a dedicated workshop at the 2017 UHMS Annual Meeting, discussion by registrants at that workshop and finally several committee meetings to formulate statements addressing points considered of prime importance to the management of DCI in the field. The committee placed particular emphasis on resolving controversies around the definition of "mild DCI" arising over 12 years of practical application of the 2004 workshop's findings, and on the controversial issue of in-water recompression. The guideline statements are promulgated in this paper. The full workshop proceedings are in preparation for publication.

Compliance with Washington State's requirement for residential carbon monoxide alarms.

Carbon monoxide (CO) poisoning is responsible for significant morbidity and mortality in the US. In response, a majority of states have passed legislation in recent years requiring the installation of residential CO alarms. There is, however, no published information evaluating compliance with such laws. Employees of a Seattle medical center were surveyed in 2008 regarding home use of CO and smoke alarms. Washington State enacted legislation requiring residential CO alarms by all residences by January 1, 2013. The survey was repeated in mid-2016 to evaluate compliance. In 2016, a total of 354 employees completed the survey and their responses were compared to an equal number of 2008 survey respondents matched by home ownership and ZIP code. Residential CO alarm use rose from 37% to 78% (p < 0.0001). Among homeowners, 78% had alarms while 80% of renters had them. Homeowners with the highest compliance (96%) had purchased their homes since January 1, 2013 while those with the lowest compliance (73%) had purchased them earlier. A majority (79%) of renters without alarms reported the reason was that their landlord did not provide one, a violation of the law. Only one-half to two-thirds of all equipped homes had the required number of either CO or smoke alarms. Use of residential CO alarms increased significantly in this study population three years after law required them. Areas for further improvement include education of landlords, tenants, and longtime homeowners about the law, as well as public education regarding the number of CO and smoke alarms needed.